Impl id() and toString()

OPEN - task 86: Create Business(Sales-Purchases) Module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/86
Make Party attribute in MappedSuperClass

OPEN - task 86: Create Business(Sales-Purchases) Module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/86
Remove obsolete code

OPEN - task 86: Create Business(Sales-Purchases) Module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/86